A 26-year-old man comes to the office due to right heel pain and swelling. He accidentally stepped on a rusty nail while working 2 weeks ago. The nail pierced his sneaker and entered his right heel. He applied over-the-counter antibiotic cream and took oral acetaminophen but continued to have pain. The patient has no other medical problems and takes no medications. He has no known drug allergies. He smokes 2 or 3 cigarettes daily and drinks alcohol occasionally. Temperature is 38.3 C (101 F), blood pressure is 140/90 mm Hg, pulse is 84/min, and respirations are 14/min. The right heel is swollen, red, warm, and tender to palpation. A small puncture wound is visible. Laboratory results show mild leukocytosis. X-ray of the right foot reveals bone changes suggestive of osteomyelitis. Which of the following is the most likely organism causing this patient's infection?

Question

A 26-year-old man comes to the office due to right heel pain and swelling.  He accidentally stepped on a rusty nail while working 2 weeks ago.  The nail pierced his sneaker and entered his right heel.  He applied over-the-counter antibiotic cream and took oral acetaminophen but continued to have pain.  The patient has no other medical problems and takes no medications.  He has no known drug allergies.  He smokes 2 or 3 cigarettes daily and drinks alcohol occasionally.  Temperature is 38.3 C (101 F), blood pressure is 140/90 mm Hg, pulse is 84/min, and respirations are 14/min.  The right heel is swollen, red, warm, and tender to palpation.  A small puncture wound is visible.  Laboratory results show mild leukocytosis.  X-ray of the right foot reveals bone changes suggestive of osteomyelitis.  Which of the following is the most likely organism causing this patient's infection?

Quizplus · Accepted Answer

Staphylococcus aureus and Pseudomonas aeruginosa are responsible for most deep infections following puncture wounds. Pseudomonas infections are particularly prevalent after puncture wounds through the sole of a shoe as the warm, moist environment is quite hospitable to this microorganism. Many puncture wound injuries remain asymptomatic, but it is estimated that >50% develop superficial cellulitis or deeper infections such as osteomyelitis. Evidence of an active infection is increased in those with skin findings of infection (edema, warmth, erythema, tenderness), leukocytosis, and fever. Radiographs are usually required to evaluate for underlying osteomyelitis when deep-penetrating injuries occur; however, bone changes consistent with osteomyelitis often take >2 weeks to form. Blood cultures are usually drawn, and bone biopsy with culture may be required to identify the microorganism. Treatment includes intravenous antibiotics (eg, ciprofloxacin, piperacillin-tazobactam) and surgical debridement. (Choices A and H) β-hemolytic streptococci and coagulase-negative staphylococci may cause wound infections but rarely cause osteomyelitis in the absence of predisposing factors such as diabetes mellitus. (Choice B) Candida osteomyelitis is sometimes seen in injection drug users but is rare following a puncture wound. (Choice C) Clostridium tetani does not cause osteomyelitis; however, this patient is at risk for tetanus and his vaccination status should be reviewed. If his status is out of date, tetanus vaccine and tetanus immunoglobulin should be administered. (Choices D and E) Escherichia coli and Klebsiella pneumoniae may cause osteomyelitis (especially in patients with diabetes mellitus), but both microorganisms are far less common than Pseudomonas in patients with puncture wounds. (Choice F) Mycobacterium tuberculosis is a rare cause of osteomyelitis in the United States but is common in developing countries. The most commonly affected bone is the spine (Pott disease). Educational objective: Patients with plantar puncture wounds through footwear are at risk for Pseudomonas aeruginosa osteomyelitis.

A 26-Year-Old Man Comes to the Office Due to Right